feat(srs): switch ladder to +3/+7 and enforce rest‑day logic

apps/api/README.md

@@ -26,10 +26,23 @@ Live at `https://srs-api.prdlk.workers.dev`.
 
 ## The ladder
 
-`new → +2 → +5 → +10 → retired`; pass advances, fail resets to `+2`.
-A problem's first-ever log enters at `+2` regardless of result. Stage names
-the NEXT review's interval. All dates are ET calendar strings anchored at
-noon UTC (`src/srs.ts`) — never raw `Date` math.
+`new → +3 → +7 → retired`; pass advances, fail resets to `+3`. A problem's
+first-ever log enters at `+3` regardless of result. Stage names the NEXT
+review's interval, and the two rungs are the same numbers as the `work/3` and
+`work/7` buckets `bun run pick` scaffolds re-solves into.
+
+**Sunday is never booked.** Topics run Mon–Fri, the gate is Saturday, and 3/7
+are chosen so a solve returns on a working day: only a Thursday solve's `+3`
+would land on the rest day, and `workingDay()` in `src/srs.ts` slides it to
+Monday. Every scheduled date in the Worker — ladder reviews, levelled
+overflow, deferred-Hard release dates — is minted by that one function, so the
+rest day cannot be booked and then swallowed by the digest's Sunday branch.
+Reviews may slip later, never earlier: pulling one back to Saturday would
+shorten the interval it exists to test. `src/srs.test.ts` sweeps the whole
+campaign calendar to prove it.
+
+All dates are ET calendar strings anchored at noon UTC (`src/srs.ts`) — never
+raw `Date` math.
 
 Blind drills draw only from topics **already learned**: scheduled in an
 earlier week (the current week's optional pool is reserved for Saturday's
@@ -83,13 +96,14 @@ bunx wrangler d1 migrations apply srs --local
 bun run dev                          # wrangler dev on :8787, local D1
 curl -X POST -H "Authorization: Bearer $LINK_KEY" \
   "localhost:8787/admin/digest?dry=1&date=2026-08-31"   # prints HTML, sends nothing
-bun test src                         # DST guard + date math
+bun test src                         # DST guards, date math, the rest-day sweep
 ```
 
-`?date=` on admin routes is the `SRS_TODAY` equivalent. The one-shot
-migration from the retired `.github/srs/srs.json` lives at
-`scripts/import-srs.ts` (`--remote` for production D1); it is re-runnable —
-import-sourced attempts are wiped and re-inserted.
+`?date=` on admin routes is the `SRS_TODAY` equivalent. Migrations are
+append-only and applied in order; `0002_ladder_3_7.sql` is the +2/+5/+10 →
+`+3`/`+7` rebuild, which also lifts every date that was sitting on a Sunday.
+The one-shot importer for the retired `.github/srs/srs.json` is gone — that
+state no longer exists, and git history is its record.
 
 ## Deploy